The rotors of rotary machines, such as turbines and compressors, generally include a number of axially stacked wheels. A number of circumferentially spaced blades are mounted in turn about the periphery of the wheels for rotation therewith. For example, compressor rotors generally include a series of individual compressor wheels stacked together with a set of tie bolts extending axially therethrough. The wheels mount the rotor blades thereon to form the compressor stages with a corresponding number of stator blades. The tie bolts typically are elongated studs that may be threaded at both ends. The tie bolts are enclosed by nuts to maintain the wheels in a stacked, assembled relationship relative to one another. A sufficient load is applied to the tie bolts to ensure that the rotor torque is carried through the stack by friction between the wheels.
It will be appreciated that any loosening of the nuts on the tie bolts would reduce the tension on the bolts and, thus, lower the torque carrying capability of the rotor. Current rotor designs thus require that the rotation of the nut relative to the bolt be prevented by redundant methods. One such method relies on friction against the threads and the stack. A second method uses a jam nut against a primary nut to prevent rotation relative to the stud. A further method uses a crimped or oblong nut barrel to increase the torque required for removal.
There thus a desire for an improved nut and bolt assembly for use with a compressor rotor and other types of rotary machines. Such an improved nut and bolt assembly preferably would be self locking, would prevent gross rotation of the bolt without adding unnecessary weight or requiring damage to expensive assembly components and the like, and would be readily accessible for inspection and disassembly.